Method and apparatus for the electrical reduction of ores.



B. G. COBB.

METHOD AND APPARATUS FOR THE ELECTRICAL REDUCTION 0F ORES.

APPLICATION man MAY 23. 1913. RENEWED oen-11.1917.

1,267,976. Patented May 28, 1918.v

2 SHEETS-SHEET l.

B. G. COBB.

METHOD AND APPARATUS FOR THE ELECTRICAL REDUCTION 0E DRES.- APPucATxoN FILED MAY23.1913. REMEWED ocT. 11.1917.

1 267,976. Patented. May28,1918..

2 SHEETS-SHEET 2.

Z0 '9 I3 I l] J7 a 64 M *HL fz ml l l l Y 1.9 i G ZJ *E172 23 UNITED STATES PATENT OFFICE.

BAYARD G. COBB, F4 DAWSON CITY, YUKON, CANADA, ASSIGNOR TO JOI-IN F. SKERRETT, HOWARD GIFFI'N, M. KIYDDER, ROBERT I. BARR, AND ELAINE INESCORT, ALL OF NEW YORK, N. Y., T0 ANDES EXPLORATION AND SlVI-ELTING CORPORA- TION, A C(312,190RATION.v OF DELAWARE.

METHOD AND APPARATUS FOR THE ELECTRICAL REDUCTION OF ORES.

Specification of Letters Patent.

Patented May as, 191s.

Application filed May 23, 191,3, Serial No. 769,351. Renewed October 11, 1917. f Serial No. 196,094.

To all whom it may concern."

lBe it lrnown that I, BAYARD G. COBB, a

citizen of the Dominion of Canada, and a resident of Dawson City, in the Territory of Yukon and DominionV ofV Canada, have invented certain Improvements in Methods and Apparatus for the Electrical Reduction of O-res, of which the following is aj specification.

This invention consists in improvements in, and methods and apparatus for, the electrical reduction of metals from their ores. Electric smelters as commonly constructed comprise essentially an ore chamber having an inner refractory lining, a fixed negative electrode at the bottom of the chamber and a carbon positive electrode mounted for vertical adjustment the middle of the ore chamber above thev negative electrode.l The charge which may consist of the ore alone or mixed with a HuX or reducing agent and'in any case must be melted by the heat ofthe arc is yplaced in the ore chamber and the current turned on with the electrodes in contact. The positive electrode is then slightly lifted to produce an arc through the broken ore which commences to melt from the heat of the Varc. As the melted and reduced ore accumulates at the bottom of the chamber the electrode is gradually raised to produce the arc in the unfused ore above until all the ore is melted.

` Apparatus of this character has been used with success with iron ores and other ores of high conductivity but when used with ores of the precious metals or other ores of low metalliferous content it has been found that unless the greatest care is used in adjusting the electrodes and in watching the fluctuations in the current the arc will frequently strike through and destroy the lining of the ore chamber before the charge is reduced.

By my invention I provide a method of balancing or controlling the arc by which the arc is absolutely prevented from striking the walls of the furnace no matter what the resistance of the mass and is also positively caused to follow different and continually changing paths through the ore wherebythe entire charge is uniformly fused. My invention also provides a mechanism whereby the control of the arc is automatically eiiected without attention from the operator. My invention includes various other features of novelty which will be more fully understood from the fol-lowing description when read in connection with the accompanying` drawings forming part of this application and wherein I have disclosed a preferred form of mechanism for carrying my invention into elfect. It will be understood however that my invention is in nowisc limited to the details of construction disclosed as the same is shown by way of eX- ample only.

In the said drawings,

Figure l is a diagrammatic partly sectional view of an electric smelter embodying my invention;

Fig. 2 is an enlarged view of a portion of the electrical control mechanism Fig. 3 is a sectional view of a modied furnace designed for ores containing volatile salts.

Fig. 4 is a transverse sectional view of Fig. 3; and Fig. 5 is a diagrammatic view illustrating a modification.

Referring now to the drawings, l indicates the ore chamber or furnace which may be constructed in the usual manner of metal with a lining la of a suitable highly refractory material. The bottom of the chamber is preferably inclined to one side to permit the reduced and molten metal to be drawn 0E through orifice 2 normally closed by a suitable plug. In the middle of the bottom of the chamber the negative electrode 3 in the form of a iiXed plug is securely set. The chamber is provided with a cover l having a swivel connection at its edge with the wall of the furnace and having at its center a guide way for the carbon 5 which constitutes the positive electrode. For adjusting the electrode a rack bar 6 is provided having suitable clamps for attaching it to the carbon, the rack meshing with a pinion 7 suitably journaled in brackets on the cover 4. Any preferred means, for example a simple crank and ratchet, may be employed for operating the pinion 7 and holding it in its adjusted position. The electrodes 3 and 5 are connected by suitable conductors 3 and 5 with a dynamo or other suitable source of current as indicated diagrammatically by the leads P and N.

The arrangement described is the usual construction of an electric smelter and the circuit through the electrodes 5 and 3 will hereinafter be referred to as the main circuit. For controlling this circuit according to my preferred method I provide two or more balancing electrodes E and E which project through the walls of the furnace at the level of the top of the charge and extend an appreciable distance into the furnace. To each of the electrodes E and E a conductor e, e respectively is attached and these conductors lead to two opposite binding posts of an automatically controlled reversing switch S shown in detail in Fig. 2. The switch comprises a suitable casing 8 having a shaft 9 rotatably mounted in the center of its top wall and projecting above its upper surface. To the upper end of the shaft 9 there is Xedly attached a cross or four armed disk 10 of ebonite or other insulating.material'hand in the end of each arm there is set a contact 11, the contacts of each two adjacent arms being connected by suitable conductors as shown in Fig. 1. In each side of the casing 8 there is set a binding post and connected with the binding posts are spring raised contacts 13, positioned to engage the contacts 1l at each quarter turn of the cross 10. As stated above the conductor e, c from the balancing electrodes E, E are connected to two of the opposite binding posts and connected to the two other posts are branches p and n from the main leads P and N. It will be obvious that when the cross is in one position of adjustment the electrodes E will be connected with the positive lead P and the electrodes E with the negative lead N and when the cross 10 is rotated a quarter turn the electrode E will be connected with the positive lead and the electrode E with the negative lead. `The shaft 9 is driven from any preferred source of power and I have shown a spring motor b v way of example. Such motor comprises a spring 14 fast at its outer end to a drum 15 attached to the shaft 9 and at its inner end to a sleeve 16 loose on the shaft and provided with a gear 17 meshing with a pinion on a winding spindle 1S at the cornerv of the casing. The shaft 9 projects below the drum 15 and has attached to its end a bevel pinion 20 meshing with a larger bevel gear 19 to a stub shaft rotatable in the side of the casing. Also attached to the stub shaft is a ratchet or escapement wheel 21 having the usual anchor 22 whose pallets 23 and 24 engage the teeth of the wheel. The stem of the anchor is bent to one side and a spring 12 acts to normally hold the pallet 23 in engagement with the fiat face of the ratchet teeth and hold the wheel stationary. The other pallet of the anchor presents an inclined face to the point of the ratchet teeth so that the passage of a tooth when the anchoris oscillated to release the ratchet will shift the anchor to bring the pallet 23 into engagement with the next tooth of the ratchet allowing the gear 19 a partial revolution and thereby through the small bevel pinion 20 rotating the shaft 9 and the cross 10 a quarter turn and reversing the polarity of the circuit through the balancing electrodes.

The operation Aof the escapement and the reversal of the balancing circuit is controlled by fluctuations in the current through the main circuit. To this end the conductor from the negative electrode 3 does not lead directly to the return lead N but is connected in series with the primary winding of an induction coil 25. The secondary winding 25a of the induction coil is connected at its opposite ends of the magnets 26 and 27 respectively of opposite polarity of a magnetic relay housed in the bottom of the Casing 8. The armatures of the magnets 26 and 27 are attached to the ends of a bar 28 pivotally suspended at each end from suitable pivots by means of arms 29 and 29. These arms are each provided with an integrally connected horizontal arm 30 and 30 whose ends lie over the stem 31 of the anchor 22. The maOnets 26 and 27 are connected with a smzll battery '32, the circuit through the battery being closed'during the-time the smelter is in operation, but as the magnets are equal in size they will balanceJ each other and have no effect on the connected armatures. The inductive coil s connected to the positive pole of one magnet and to the negative pole of the other, so that whenever current flows in the coil such current will act in opposition to the battery current of one magnet and will increase the current strength of the other magnet. When however there is al change in the strength of the current through the main circuit, there will be induced in the secondary winding of the induction coil a current impulse depending in direction on whether the change in the main circuit is an increase or decrease in current strength. In either direction however the effect of the induced current will be to increase the current around one magnet of the relay and decrease it through the other so that the relay is thrown out of balance and the connected armatures attracted by the strong magnet. Movement of the armature in either direction will depress one of the arms 30, 30 thereby operating the anchor of the escapement to permit the reversing switch a quarter revolution. The spring l2 is strong enough, when the current through the magnets again be:

comes the saine, to return the armature to its' central neutral position and putj the relay agrain inlbalzjinee.' y i 4vThe operation of the apparatus as axvhcle will noiv be described. AfterV thev furnace isfcliarged, the main electrodes are somewhat separated to canse the current to arc through the ore at the bottom thereby commencing the fusing of the-ore. DuringA the first part of the` operation there will be practically nto current flowing through the balancing circuit, but as the sinelting proceeds and the electrodes are. further separated, the resistance greatly increases. llnderthese conditions the balancing' electrodes become effective. Instead of al pathof least resistance through the lining' of the furnace the current from. the main positive electrode Will in part pass through the ore on lthe sur of the charge to the then negative balancing electrode, the balancing electrodes beingv positioned from the main electrode a distance such as to present a path of less resistance than through the wall of the furnace. It will of course be understood that the action of the are through different portions of the charge causes the ore to frequently shift in the furnace so that the paths of the current between the main electrodes, producing as it were a didusion of the current throughout the mass with frequent changes in resistance, which through the mechanism described reverse the polarity of the circuit through the balancing electrodes. It will be understood that the mechanism of the commutator is sufficiently delicate to be actuated by the current induced by the change in resistance resulting from the displacement of a single lump of ore.

The diffusion of the current through the charge is greatly augmented by the balancing electrodes constantly changing the path of the shunt circuit as will be obvious, but my invention is not to be understood as limited to this arrangement shown, as the balancing electrodes may be both of fixed negative polarity and effectively prevent the destruction of the furnace lining. Such arrangement is not however as desirable as that described, as it tends to a concentration of the current in fixed portions of the charge.

It will be clear also that the balancing electrodes may be connected in parallel and the polarity of'both changed from positive to negative on fluctuations of the main circuit. Also a plurality of electrodes may bc used as shown in Fig. 5 with the alternate electrodes connected in parallel to provide a better diffusing of the current. This. arrangement is particularly suitable for large furnaces.

In Figs. 3 and l I have shown an arrangement which is particularly adapted for ores containing valuable volatile ingredients In this modification the ore chamber is provided withy apipel 50 leading to a suitable stack or other chamber of suilicient extent and proper material. to provide a subliming a rea for the `volatile material.

The volatile ingredients as they are clevated by the heat of the furnace are carried into the stach by a blastof air preff erably directed into the chamber through tangential nozzles 51 from a suitable blower. The air may be hot or cold as necessary to secure the desired oxidation of the i volatiles.

One important advantage of my invention that may be mentioned is that it enables refractory ore of a high electrical resistance to be reduced entirely by electrolysis without the use of iiuxes or chemical reducing agents. In elect qic furnaces vas heretofore constructed it is not practical to treat ore of this nature Without such fluxes or reducing agents, because of the liability of the furnace to be destroyed by the current required when such ingredient-s are not employed. By my process the ore alone is placed in the furnace and is first melted by the arc and then the current continued through the fused ore to effect the purely electrical separation of the metal. A

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

l. The method of fusing metallic ores which consists in producing an electric arc between a positive and a. negative electrode of one circuit Within the crushed ore and passing an electric current between electrodes of a second circuit at the surface of the ore at predetermined distances from the positive electrode of the first circuit,l

and causing the polarity of the electrodes of the second circuit to frequently vary.

2. In an apparatus of the class described, the combination of an ore chamber, a pair of main electrodes for producing an arc Within the ore in said chamber, a secondary circuit comprising` a pair of electrodes near the surface of said charge, and means for reversing the current through said second ary circuit.

3. In an apparatus of the class described, the combination of an ore chamber, a pair of main electrodes producing an are Within the ore in said chamber. a secondary circuit comprising a pair of electrodes in contact with the ore in said chamber. means for reversing the circuit through said electrodes and means actuated by fluctuations in the current to said main circuit for actuating said reversing means.

4:. In an apparatus of the class described, the combination of an ore chamber, a pair of main electrodes for producing an arc Within the ore in said chamber supplemenF tary electrodes in. contact 'With the ore in said chamber' and means for reversing the polarity of said supplementary electrodes.

5. In an apparatus of the class described, the combination of an ore chamber, a pair of main electrodes for producing an are in the ore in said chamber, supplementary electrodes also in Contact with the ore in said chamber, means for reversing the polarity of said supplementary electrodes and means operated by either increases or decreases of the current strength through said main circuit for operating said reversing means.

6. In an apparatus of the class described, the combination of an ore chamber, a pair of main electrodes in the ore chamber, supplementary electrodes also within said balancing of said relay and thereby releasing said eseapement. n

Signed at New York, in the county of New York and State ot New York, this 17th day of May, 1913.

'BAYARD e. COBB.

Witnesses:

W. B. MoRToN, L. E. JOHNSTON.

Copies of this patent may be obtained for ive cents each, by addressing the Commissioner of Patents, Washington, D. G. 

